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With a 3rd night of data added, here's another process of the Veil nebula.

34 x Ha, Astronomik 12nm filter, modified Canon 450D

28 x SII, Astronomik 12nm filter, modified Canon 450D

61 x OIII, Astronomik 12nm filter, standard Canon 600D

All 4m subs, with flats.


Pseudo real colour created by adding all the above as RGB.


Hubble palette: R=SII, G=Ha, B=OIII

I think this just isn't a subject that lends itself to the Hubble palette.

Also I'm not happy with my processing. I went heavy on star and noise reduction, but that's blurring the fine lines of the nebula too. I suspect this is one I'll revisit again. The noise levels of the Ha and SII are visible stronger than the OIII, so I think I'll spend yet another night on it some time to boost that some more.

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I imagine this would look good made as a 3D picture with 3D glasses. Certainly the left part looks like it has three dimensions not two! And the sky looks darker in the second picture somehow. Maybe there's just a bigger contrast between black and magneta than between black and purple.

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Following a comment by Olly about doing a summed mono version, I thought I'd give it a quick go. Not having to worry about colour noise, I could be more aggressive at bringing out the faint stuff. I like what I saw, and thought, how would it look if I used that as the L channel for LRGB recombination? The result is sampled above, which can be clicked through to a bigger version (it was 1920 wide but the forum gallery seems to have shrunk it to 1600).

Also I felt like a change of palette, so it's in R=Ha, G=SII, B=OIII with little post adjustment. The noise wasn't as good as I hoped, probably due to the synthetic L channel having correlated noise since it was created from the individual colour channels. Perhaps with more selective channel noise reduction there's more potential left in this technique. Or maybe I could throw all the different channel data into an "anything goes" stack for L channel? That might be an overnight job if I ever dare do it...

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Very interesting :) And I see what you mean by not getting all the bottom nebulosity in the frame as you mentioned in my thread. Is that with ED80 with 0.85x FR/FF?

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This is with a Sigma 120-300mm f/2.8 OS lens wide open. If you want pinpoint stars, this wont be your optic of choice!

Thanks :) Silly me - of course its a lens not a scope - must be getting tired :D

May not be the best optic but your images are very sharp, none the less :)

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Gina, showing the images scaled down does a good job of hiding the optical nasties :)

Keith, well, I was getting SII, although it was pretty low down. Following are samples of the stack I did of each. Both were stacked using the same settings, and the output below have the same stretch. I never noticed before the SII seems to have a higher background level. I don't have an explanation for that, but could skyglow be higher at SII wavelengths than Ha, even if they are close? The sensor sensitivity should be lower at SII anyway, so if anything the level might be lower, and I don't think anything would have boosted the background.


Sample Ha


Sample SII

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Cheers for posting that, shooting at F2.8 is the crucial difference I think, I'm shooting at F5.3 so im probably fighting a losing battle against the noise floor with too little signal with SII. Good to know that SII is possible though with the modded 450d, maybe Gina should get that SII clip afterall :)

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I don't think so TBH though I am planning to cool my widefield camera. That would make it a bit more feasible. But I'm trying NOT to spend on anything of poorer benefit - I'd rather put the funds towards an Atik 314L+. This doesn't mean I shall be abandoning my DSLR efforts - there is room for both. The Atik would be for smaller DSOs and particularly NB when an SII filter will definitely be considered, with the main camera on the scope covering larger objects in colour. I shall keep a widefield camera for Ha, OIII and use as a finder. ATM I have a spare modded DSLR (1100D) which I could possibly set up as a side-by-side setup - Ha and OIII until I sell the spare camera.

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Thanks all. I am quite pleased I'm making fair use of a DSLR for imaging, although I still want to add more data to reduce the noise further on this one, which might allow me to dig a bit deeper too.

Also as I want to concentrate on narrowband, a CCD is a natural upgrade for when I decide to throw enough money at it. And a new set of filters, and new optics... and... :D

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I expect to add an astro CCD camera to my kit when I've saved up enough. Might manage it before the end of winter :D Maybe earlier depending if any unexpected expenses crop up.

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My problem is if I go CCD which is expensive enough on its own, I really need a new set of filters too. I'm rather attracted to a set of Astrodon's 3nm ones to help me through light pollution as best I can.

Why wouldn't you be able to use your Astrodon filters?

I have a filter wheel building project on the back burner and expect to buy some 1.25" Baader filters in due course - probably Ha and OIII first then maybe SII and an LRGB set.

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I'm confused... Do you mean Astrodon 3nm filters as in your earlier post or Astronomik clip filters which surely aren't that narrow? The narrowest from Modern Astronomy where I bought mine, are 6nm bandwidth - do Astronomik actually make 3nm ones?

I'm keeping my Astronomik filters for widefield use and will buy new filters for NB CCD use. You could make a filter carousel to take clip-in type filters.

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